The present invention relates to a restraining device for an occupant of a vehicle.
German patent document DE 44 11 184 C2 discloses a passenger restraint belt system for use with a seat fitted in a vehicle. It comprises a seat belt for securing a passenger in a seated position on the seat, a seat-belt tightener, which reacts to a control signal in order to restrain the passenger on the seat. A device is provided for measuring the distance and speed of the vehicle in relation to an object and a device for calculating a time after which a vehicle collision with the object is anticipated. A control unit generates a control signal, which increases the force of the seat-belt tightener in good time, if a vehicle collision is anticipated, and a second control signal, which reduces the force of the seat-belt tightener if no vehicle collision is anticipated.
The controllable seat-belt tightener is embodied as a preloader, which prior to the vehicle collision is effective only up to a predetermined pretightening force, and a further seat-belt tightener is provided, which is triggered if a vehicle collision is detected. The belt is tightened by retracting the belt latch mechanism with a total force. (FIG. 1 shows this process.) In so doing the belt latch mechanism divides the belt into two parts, in which the tightening component forces act in opposition to one another relative to the belt and are in each case less than the total force. As a result, only a slight, barely perceptible pressure is exerted on the upper body of the passenger.
Although in the case of danger, this passenger restraint belt system reduces any slack in the passenger seat belt, it does not act to provide the passenger with any indication.
One object of the invention, therefore, is to provide a simple and improved restraining device, which reduces any seat-belt slack of a vehicle occupant.
This and other objects and advantages are achieved by the restraining device according to the invention, which has a belt that can be drawn out or retracted by a lockable retractor, and a reversible seat-belt tightener. In the case of an impending but still avoidable first event, the reversible seat-belt tightener automatically exerts and maintains a first tightening force on the belt and/or reduces the first tightening force if the first event is no longer impending. In the case of an impending, no longer avoidable second event, it automatically exerets a second tightening force on the belt which is greater than the first tightening force. The first tightening force and the second tightening force act constantly in the retracting direction.
This restraining device reduces any slack in the seat belt of the vehicle occupant, and also indicates the risk of an impending but still avoidable first event to the vehicle occupant in the form of a tactile warning. The tightening in one direction relative to the belt means that the magnitude of the tightening force is identical in all areas of the belt and is clearly perceptible by the occupant.
Should one of the events occur, the occupant is optimally protected against any acceleration in that, in the case of a third event being detected, the seat-belt tightener automatically exerts a third tightening force on the belt, which is greater than the second tightening force. The third tightening force preferably acts exclusively in the retracting direction. In the case of the third force also, an identical force thereby acts in all areas of the belt. The third force is preferably exerted by the triggering of an explosive charge.
In other words, the first, second and third events represent the severity of the risk of an impending accident. As the risk of an accident increases, the force to be exerted on the belt is steadily increased in the form of the associated first and second tightening forces, and is explosively increased in the form of the third tightening force when an accident is identified.
In one possible embodiment, in the case of an impending but avoidable first event, the seat-belt tightener exerts a fourth tightening force, the magnitude of which lies between the first and second forces, after a first delay interval which commences after exertion of the first tightening force and prior to exertion of the second tightening force. A fourth event is associated with the fourth tightening force. It is defined as a point in time prior to the second event and after the delay interval following the exertion of the first force has elapsed.
In another embodiment, in the case of a first event, the seat-belt tightener exerts a fourth tightening force, which is followed immediately by a delay interval prior to exertion of the second tightening force and the magnitude of which lies between the first force and the second force.
Both of these variants of the intermittent tightening make the indication given to the occupant even more perceptible. If there is sufficient time before the advent of the second event, the exertion of the fourth tightening force is repeated with an increased fourth tightening force after a further delay interval.
In this case the fourth tightening force acts exclusively in the retracting direction. In the case of the fourth force also, an identical force thereby acts in all areas of the belt.
In a preferred embodiment the seat-belt tightener is arranged in the area of the retractor, which facilitates tightening in the retracting direction. This is particularly feasible, with little outlay, if the seat-belt tightener uses the tightening forces to displace the retractor.
In an advantageous embodiment the retractor is automatically locked prior to the exertion of a tightening force, and the locking of the retractor is automatically canceled prior to the reduction of this tightening force. In this way the requisite tightening distances are minimized. In addition, the tightening is canceled as soon as the risk of the relevant or ensuing event has passed. The occupant is thereby able to move more freely.
In another possible variant, the seat-belt tightener uses the tightening forces to retract the belt into the retractor. The rotating movement means that this variant takes up less space than a displacing movement. The belt is suitably embodied as a three-point belt, thereby providing a simple and highly reliable means of restraint.
In an advantageous embodiment at least one radar distance-measuring device is used to detect an impending event. This permits a precise and rapid calculation of the distances and relative speeds and thereby gives the restraining device a short reaction time.
In a preferred embodiment the restraining device is arranged on a driver's seat in the vehicle. Given an impending event, the driver is consequently prompted to react accordingly, for example to brake or brake more sharply, or to undertake an evasive maneuver.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.